Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphorylation of proteins catalysed by protein kinases is associated with central functions in growth and proliferation of the eukaryotic cell, and kinases are particularly important in the signal transduction pathways. Enterobacterial protein kinases are structurally and functionally different from eukaryotic protein kinases, and no prokaryotic kinase has so far been described implicating a direct role for this activity in virulence. Virulent Yersinia possess a common virulence plasmid that encodes a number of secreted proteins (Yops), of which YopH has protein-tyrosine phosphatase activity with a key function in the block of phagocytosis by the pathogen. Here we report that the virulence plasmid of Yersinia pseudotuberculosis encodes a secreted protein kinase (YpkA) with extensive homology to eukaryotic Ser/Thr protein kinases. Specific mutants of ypkA resulted in avirulent strains. Thus, YpkA is, to our knowledge, the first reported prokaryotic secreted protein kinase involved in pathogenicity, presumably by interfering with the signal transduction pathways of the target cell.
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PMID:A secreted protein kinase of Yersinia pseudotuberculosis is an indispensable virulence determinant. 844 68

Campylobacter jejuni isolates obtained from human and animal sources showed different invasion levels into human embryonic intestinal (INT-407) cells. There was no significant relation between the degree of invasion and cytotoxins production. The depolymerization of both microfilaments by cytochalasin-D and microtubules by colchicine, demecolcine and nocodazole or stabilization of microtubules by paclitaxel reduced the invasiveness of C. jejuni, although microfilament depolymerization showed greater inhibition than microtubule depolymerization. Interference with receptor-mediated endocytosis by G-strophanthin and monodansylcadaverine and inhibition of endosome acidification by monensin reduced the number of viable intracellular C. jejuni cells. Furthermore inhibition of only host protein kinases by staurosporine, but not phosphoinositide 3-kinase by wortmannin or protein kinase-C by calphostin-C, significantly reduced invasion of epithelial cells by C. jejuni. These data suggest that the internalization mechanism triggered by C. jejuni is strikingly different from the microfilament-dependent invasion mechanism exhibited by many of the well-studied enteric bacteria such as enteroinvasive strains of Escherichia coli, Salmonella typhimurium, Shigella flexneri, Yersinia enterocolitica and Yersinia pseudotuberculosis.
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PMID:Uptake pathways of clinical and healthy animal isolates of Campylobacter jejuni into INT-407 cells. 1106 67

The Yersinia protein kinase A (YpkA) is injected into host cells by the yersinial type three secretion system (TTSS). YpkA is widely believed to function within the host cell based on the fact that its kinase domain is clearly homologous to eukaryotic Ser/Thr kinases and that its enzymatic activity, when assayed in vitro, is dependent on eukaryotic-derived host factors. Whether this activity is required for virulence has not been addressed. Here, we report that a Yersinia pseudotuberculosis strain expressing a kinase-inactive YpkA(D270A) variant is greatly attenuated in the mouse model of infection compared to the isogenic wild-type strain. The ypkA(D270A) mutant strain was likewise attenuated in a cell culture infection assay indicating that the kinase activity of YpkA enhances the viability of host cell-associated bacteria. To begin to understand what cellular activities are targeted, we expressed YpkA and its variants in two different yeast model systems. In agreement with previous studies, we found that when rapidly induced and expressed at high levels in Saccharomyces cerevisiae, YpkA-mediated toxicity occurred extremely swiftly. Under these conditions toxicity was dependent on the structurally distinct GTPase-binding domain of YpkA and was entirely independent of its kinase activity. Therefore, to probe for kinase-dependent effects we expressed YpkA and its kinase-inactive variant at comparatively moderate levels in the fission yeast Schizosaccharomyces pombe. S. pombe is particularly well suited for actin cytoskeletal studies due to its easily quantifiable, well defined pattern of actin localization. S. pombe transformed with a wild-type YpkA-encoding plasmid displayed a pronounced actin mislocalization phenotype, the severity of which was directly proportional to the level of YpkA expressed in the cell. In cells expressing the kinase-inactive YpkA variant, the degree of actin mislocalization was reduced, but not entirely abrogated, suggesting that YpkA affects the eukaryotic cytoskeleton through kinase-dependent and kinase-independent mechanisms. Collectively, our yeast-derived results show how critical expression levels and exposure periods are for assaying virulence factor activities in heterologous model systems. More generally, our finding that the 'eukaryotic-like' kinase domain of YpkA is important for virulence illustrates how a bacterium can utilize a host-like factor or activity in order to enhance its survival following host cell contact.
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PMID:The Ser/Thr kinase activity of the Yersinia protein kinase A (YpkA) is necessary for full virulence in the mouse, mollifying phagocytes, and disrupting the eukaryotic cytoskeleton. 1662 27

Yersinia spp. cause gastroenteritis and the plague, representing historically devastating pathogens that are currently an important biodefense and antibiotic resistance concern. A critical virulence determinant is the Yersinia protein kinase A, or YpkA, a multidomain protein that disrupts the eukaryotic actin cytoskeleton. Here we solve the crystal structure of a YpkA-Rac1 complex and find that YpkA possesses a Rac1 binding domain that mimics host guanidine nucleotide dissociation inhibitors (GDIs) of the Rho GTPases. YpkA inhibits nucleotide exchange in Rac1 and RhoA, and mutations that disrupt the YpkA-GTPase interface abolish this activity in vitro and impair in vivo YpkA-induced cytoskeletal disruption. In cell culture experiments, the kinase and the GDI domains of YpkA act synergistically to promote cytoskeletal disruption, and a Y. pseudotuberculosis mutant lacking YpkA GDI activity shows attenuated virulence in a mouse infection assay. We conclude that virulence in Yersinia depends strongly upon mimicry of host GDI proteins by YpkA.
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PMID:Yersinia virulence depends on mimicry of host Rho-family nucleotide dissociation inhibitors. 1695 67

Pathogenic bacteria of the genus Yersinia employ a type III secretion system to inject bacterial effector proteins directly into the host cytosol. One of these effectors, the Yersinia serine/threonine protein kinase YpkA, is an essential virulence determinant involved in host actin cytoskeletal rearrangements and in inhibition of phagocytosis. Here we report that YpkA inhibits multiple Galphaq signaling pathways. The kinase activity of YpkA is required for Galphaq inhibition. YpkA phosphorylates Ser47, a key residue located in the highly conserved diphosphate binding loop of the GTPase fold of Galphaq. YpkA-mediated phosphorylation of Ser47 impairs guanine nucleotide binding by Galphaq. Y. pseudotuberculosis expressing wild-type YpkA, but not a catalytically inactive YpkA mutant, interferes with Galphaq-mediated signaling pathways. Identification of a YpkA-mediated phosphorylation site in Galphaq sheds light on the contribution of the kinase activity of YpkA to Yersinia pathogenesis.
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PMID:Identification of a molecular target for the Yersinia protein kinase A. 1753 6

The cycle inhibiting factor (Cif) produced by enteropathogenic and enterohemorrhagic Escherichia coli was the first cyclomodulin to be identified that is injected into host cells via the type III secretion machinery. Cif provokes cytopathic effects characterized by G(1) and G(2) cell cycle arrests, accumulation of the cyclin-dependent kinase inhibitors (CKIs) p21(waf1/cip1) and p27(kip1) and formation of actin stress fibres. The X-ray crystal structure of Cif revealed it to be a divergent member of a superfamily of enzymes including cysteine proteases and acetyltransferases that share a conserved catalytic triad. Here we report the discovery and characterization of four Cif homologs encoded by different pathogenic or symbiotic bacteria isolated from vertebrates or invertebrates. Cif homologs from the enterobacteria Yersinia pseudotuberculosis, Photorhabdus luminescens, Photorhabdus asymbiotica and the beta-proteobacterium Burkholderia pseudomallei all induce cytopathic effects identical to those observed with Cif from pathogenic E. coli. Although these Cif homologs are remarkably divergent in primary sequence, the catalytic triad is strictly conserved and was shown to be crucial for cell cycle arrest, cytoskeleton reorganization and CKIs accumulation. These results reveal that Cif proteins form a growing family of cyclomodulins in bacteria that interact with very distinct hosts including insects, nematodes and humans.
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PMID:Cycle inhibiting factors (CIFs) are a growing family of functional cyclomodulins present in invertebrate and mammal bacterial pathogens. 1930 57